1. Field of the Invention
This invention relates to a liquid discharging head having a movable member displaceable by the utilization of the creation of a bubble occurring by heat energy being caused to act on liquid, a head cartridge, a liquid discharging apparatus and a liquid discharging method using the liquid discharging head.
Particularly, the present invention relates to a liquid discharging head for controlling the discharge state of liquid by a movable member displaceable by pressure resulting from the disappearance of a bubble, a head cartridge, a liquid discharging apparatus and a liquid discharging method using the liquid discharging head.
2. Related Background Art
As a method of steeply varying the pressure in a liquid flow path having a discharge port for discharging liquid therethrough to thereby discharge the liquid in the liquid flow path through the discharge port, there is known a bubble jet recording method of giving energy such as heat to liquid to thereby cause a state change accompanied by a steep volume change (the creation of a bubble) in the liquid, and discharging the liquid from a discharge port by an action force based on this state change, and causing the liquid to adhere to a recording medium to thereby effect image formation. In a recording apparatus using this bubble jet recording method, as disclosed in U.S. Pat. No. 4,723,129, etc., there are generally disposed a discharge port for discharging liquid, a liquid flow path communicating with this discharge port, and an electrothermal converting member as energy generating means for discharging liquid disposed in the liquid flow path.
According to such a liquid discharging method, images of high dignity can be recorded at a high speed and with low noise, and in a head carrying out this liquid discharging method, discharge ports for discharging the liquid can be disposed highly densely, and this leads to many excellent advantages that recorded images of high resolution and further, colored images can be easily obtained by a compact apparatus. Therefore, in recent years, this bubble jet recording method has been utilized in many office machines such as printers, copying apparatuses and facsimile apparatuses, and has further come to be utilized even in an industrial system such as a textile printing apparatus.
Also, in such a liquid discharging method, the condition for driving the electrothermal converting member is a simple rectangular pulse, and this leads to the feature that there is obtained a very stable discharging state.
On the other hand, as another liquid discharging method, there is known a piezo system whereby electricity is applied to a piezoelectric element and the deformation thereof is utilized to discharge liquid from a discharge port.
In such a liquid discharging method, the volume of a nozzle storing liquid therein can be changed to both an increase side and a decrease side and therefore, depending on the driving condition of the piezoelectric element, it is possible to change the discharge state of the liquid.
Now, in recent years, gradation recording in which the discharge amount is variably controlled has been effected with a view to improve the quality of image. However, if an attempt is made to variably control the discharge amount in the prior-art liquid discharging method as described above, the driving condition and circuit become complicated and the mechanical reaction after the operation of the piezoelectric element necessarily occurs, and this adversely affects the discharge. Therefore, in such a liquid discharging method, control for repeating a stable discharge state must be effected, and this leads to the problem that the control method becomes complicated.
Particularly, the influence of this reaction is great in an operation which is not accompanied by discharge and therefore, it is practically impossible to effect the control as described above. Further, in the piezoelectric element itself, the structure thereof is complicated and the amount of displacement thereof is small and therefore, to discharge the liquid, it is necessary to make the area of the piezoelectric element relative to the liquid flow path large, and this is impossible to realize in a system wherein parts are disposed highly densely as in the bubble jet system.